[SECURITY] CVE-2026-42498 Apache Tomcat - WebSocket authentication header exposure

CVE-2026-42498 Apache Tomcat - WebSocket authentication header exposure

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.0-M1 to 11.0.21
Apache Tomcat 10.1.0-M1 to 10.1.54
Apache Tomcat 9.0.2 to 9.0.117
Older, unsupported versions may also be affected

Description:
If a WebSocket request was redirected after authentication, Tomcat's 
WebSocket client would present the most recent authentication header to 
the redirect target host.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.22 or later
- Upgrade to Apache Tomcat 10.1.55 or later
- Upgrade to Apache Tomcat 9.0.118 or later

Credit:
This issue was identified by lokerxx

History:
2026-05-12 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html